Linux Virtualization - Aug 2010 - [PATCH 2/5] staging: hv: Fixed lockup problem with bounce_buffer scatter list - RESEND

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Fixed lockup problem with bounce_buffer scatter list which caused 
crashes in heavy loads.

Signed-off-by:Hank Janssen <hjanssen at microsoft.com
Signed-off-by:Haiyang Zhang <haiyangz at microsoft.com

---
 drivers/staging/hv/storvsc_drv.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/hv/storvsc_drv.c b/drivers/staging/hv/storvsc_drv.c
index 3b9ccb0..169d701 100644
--- a/drivers/staging/hv/storvsc_drv.c
+++ b/drivers/staging/hv/storvsc_drv.c
@@ -615,6 +615,7 @@ static int storvsc_queuecommand(struct scsi_cmnd *scmnd,
 	unsigned int request_size = 0;
 	int i;
 	struct scatterlist *sgl;
+	unsigned int sg_count = 0;
 
 	DPRINT_DBG(STORVSC_DRV, "scmnd %p dir %d, use_sg %d buf %p len %d "
 		   "queue depth %d tagged %d", scmnd, scmnd->sc_data_direction,
@@ -697,6 +698,7 @@ static int storvsc_queuecommand(struct scsi_cmnd *scmnd,
 	request->DataBuffer.Length = scsi_bufflen(scmnd);
 	if (scsi_sg_count(scmnd)) {
 		sgl = (struct scatterlist *)scsi_sglist(scmnd);
+		sg_count = scsi_sg_count(scmnd);
 
 		/* check if we need to bounce the sgl */
 		if (do_bounce_buffer(sgl, scsi_sg_count(scmnd)) != -1) {
@@ -731,15 +733,16 @@ static int storvsc_queuecommand(struct scsi_cmnd *scmnd,
 					      scsi_sg_count(scmnd));
 
 			sgl = cmd_request->bounce_sgl;
+			sg_count = cmd_request->bounce_sgl_count;
 		}
 
 		request->DataBuffer.Offset = sgl[0].offset;
 
-		for (i = 0; i < scsi_sg_count(scmnd); i++) {
+		for (i = 0; i < sg_count; i++) {
 			DPRINT_DBG(STORVSC_DRV, "sgl[%d] len %d offset %d\n",
 				   i, sgl[i].length, sgl[i].offset);
-			request->DataBuffer.PfnArray[i] -				
page_to_pfn(sg_page((&sgl[i])));
+			request->DataBuffer.PfnArray[i] = 
+				page_to_pfn(sg_page((&sgl[i])));
 		}
 	} else if (scsi_sglist(scmnd)) {
 		/* ASSERT(scsi_bufflen(scmnd) <= PAGE_SIZE); */
-- 
1.6.0.2

On 09/01/2010 09:38 AM, Joe Perches wrote:
> On Tue, 2010-08-31 at 11:13 -0700, Hank Janssen wrote:
> 
>> diff --git a/drivers/staging/hv/storvsc_drv.c
b/drivers/staging/hv/storvsc_drv.c
> []
>> -			request->DataBuffer.PfnArray[i] >> -				
page_to_pfn(sg_page((&sgl[i])));
>> +			request->DataBuffer.PfnArray[i] = 
>> +				page_to_pfn(sg_page((&sgl[i])));
> 
> I did a bit of a doubletake reading this last change.
> 
> This isn't actually a part of your fix and it introduces
> a whitespace error.
> 
I will resubmit this patch and clean up the whitespace error.

When change the code I normally also change the indentation to the
correct format for that area of the code. That is how the whitespace
snuck in there.

Thanks,

Hank.

On Tue, 2010-08-31 at 11:13 -0700, Hank Janssen wrote:
> diff --git a/drivers/staging/hv/storvsc_drv.c
b/drivers/staging/hv/storvsc_drv.c
[]
> -			request->DataBuffer.PfnArray[i] > -				
page_to_pfn(sg_page((&sgl[i])));
> +			request->DataBuffer.PfnArray[i] = 
> +				page_to_pfn(sg_page((&sgl[i])));
I did a bit of a doubletake reading this last change.

This isn't actually a part of your fix and it introduces
a whitespace error.